The present invention relates generally to mechanisms for interconnecting electrical leads and electrical medical devices, and more particularly to systems and methods of interconnecting implantable electrical leads and implantable medical electrical devices such as pacemakers, nerve stimulators, implantable defibrillators, implantable monitors and so forth.
Cardiac stimulation systems commonly include a pulse generating device, such as a pacemaker or implantable cardioverter/defibrillator that is electrically connected to the heart by at least one electrical lead. An electrical lead provides an electrical pathway between the pacemaker, connected to the proximal end of the lead, and myocardial tissue, in contact with the distal end of the lead. In such a manner electrical pulses emitted by the pacemaker travel through the lead and stimulate the heart. Intrinsic cardiac signals may be sensed by electrodes located on the lead and conducted via the lead to sense amplifiers in the device for monitoring the heart""s natural rhythm.
As implantable electrical devices have increased in their complexity, there have been an increasing variety of electrical lead systems developed for use in conjunction with these devices. Nowhere is this more apparent than in the context of implantable cardioverter/defibrillators, which may include two, three or more leads located for sensing or stimulating up to all four heart chambers. The leads themselves may carry one, two, three, or more electrodes, and may employ a variety of different electrical connector configurations and types. As a result, manufacturers of implantable pacemakers and cardioverter/defibrillators have had to produce their products with a variety of connector block configurations, capable of use with different lead systems. For example, Medtronic, Inc. presently manufactures implantable cardioverter/defibrillators with four basic connector designs, designated configurations xe2x80x9cBxe2x80x9d, xe2x80x9cCxe2x80x9d, xe2x80x9cDxe2x80x9d, and xe2x80x9cExe2x80x9d. The xe2x80x9cBxe2x80x9d configuration includes three 6.5 mm connector bores for receiving high voltage electrical lead connectors of the type used to couple to cardioversion/defibrillation electrodes and one IS-1 compatible 3.2 mm in-line electrical connector bore for receiving an IS-1 electrical lead connector of the type generally used to couple to cardiac pacing and sensing electrodes. The xe2x80x9cCxe2x80x9d configuration includes a single 3.2 mm xe2x80x9cDF-1xe2x80x9d connector bore for receiving high voltage electrical lead connectors used to couple to cardioversion/defibrillation electrodes and a single IS-1 connector bore. The xe2x80x9cDxe2x80x9d configuration includes three DF-1 connector bores and one IS-1 connector bore. The xe2x80x9cExe2x80x9d configuration includes two 6.5 mm connector bores and two 5 mm connector bores for receiving electrical lead connectors used to couple to individual cardiac pacing and sensing electrodes.
As is apparent from the above discussion, multiple connector block types are necessitated both by the use of multiple connector standards and the desire to connect a varying number of lead systems to a given device. The situation is complicated even further by the use of non-standard connector systems. For example, it has been increasingly common to utilize small-diameter guide catheters to deliver leads having a diameter of 7 French or less to a desired implant site. Down-sized cardiac lead designs have been developed in an effort to make the leads more easily implantable in narrow vessels and to allow multiple leads to be implanted. After lead placement is completed, the catheter must be withdrawn from the patient""s body. However, if the catheter has a small inner diameter, the inner lumen of the catheter cannot accommodate a standard-size lead connector such as one conforming portions. Such slittable or splittable catheters are more expensive to manufacture, and require the additional slitting step to remove. To remedy this problem, the lead may instead include a small-diameter, non-standard connector that easily fits within the catheter lumen, allowing the catheter to be readily withdrawn from the body. This non-standard connector has the drawback of necessitating the use of an even larger number of connector block configurations.
Traditionally, incompatibility between the configuration of the connector block and the connector assemblies on the implanted leads has been addressed by means of adapters. Typically, these adapters take the form of a relatively short lead which at one end has a connector assembly which may be inserted into one or more bores on the connector block on the implantable device and at the other end has one or more connector bores capable of receiving the connector assembly or assemblies on the electrical leads to be used with the device. These adapters are bulky and add substantially to the size of the pocket in which the device is to be implanted. In addition, they tend to require a number of additional steps to be performed by the physician in order to couple the leads to the implanted device, and are thus generally seen as undesirable. Such adapters are disclosed in U.S. Pat. No. 5,000,177, issued to Hoffmann, and U.S. Pat. No. 5,328,442, issued to Levine. Some adapters, such as disclosed in U.S. Pat. Nos. 5,050,602 issued to Osypka and 5,060,649 issued to Hocherl et al. even required removal of the connector assembly of the lead as part of the connection process.
Another approach to resolving lead/device incompatibility problems is the upsizing adapter. An upsizing adapter is used to convert a smaller-diameter lead connector to a larger-sized standard connector bore. This is particularly useful when dealing with leads having smaller connectors for use with non-splittable guide catheters. As discussed above, a smaller lead connector allows guide catheters to be easily withdrawn over the lead proximal end after the lead is properly positioned in a desired location. After the guide catheter has been removed from the body, the upsizing adapter may be connected to the proximal lead end to allow the lead to be coupled to a device having a standard connector block.
One example of an upsizing adapter is shown in U.S. Pat. No. 5,007,864, issued to Stutz Jr. This patent discloses an adapter to convert a smaller-diameter unipolar lead system to a larger connector block. Although this system allows a small-diameter lead to be used with a non-splittable catheter, this system has a limitation of not being adaptable for use with bipolar leads.
Another example of an up-sizing adapter is disclosed in U.S. Pat. No. 4,583,543, issued to Peers-Trevarton. While this system is adaptable for use with bipolar lead systems, it can only be used with a lead having a connector pin that is smaller than the connector bore. That is, it is not adaptable for use with a lead having a standard connector pin size but a non-standard connector body size.
What is needed, therefore, is an improved system and method for allowing a lead connector of a first size to couple to a larger-sized device connector, and that addresses the foregoing problems.